Diffie-Hellman for the layman

#1

Post by boris1 » Thu, Apr 29, 2021, 6:13 AM UTC

Diffie-Hellman for the layman
borisreitman.medium.com

Re: Diffie-Hellman for the layman

#2

Post by avmich » Sat, May 01, 2021, 2:48 AM UTC

So this doesn't unfortunately work with a man in the middle?

That is, how email exchange can be guaranteed to work properly, and MITM won't insert his email in the middle of the process?

Re: Diffie-Hellman for the layman

#3

Post by spekcular » Sat, May 01, 2021, 3:14 AM UTC

avmich wrote: post #2

So this doesn't unfortunately work with a man in the middle? That is, how email exchange can be guaranteed to work properly, and MITM won't insert his email in the middle of the process?

Yes, exactly. This is why real-world systems additionally include some kind of authentication protocol.

Reference: https://en.wikipedia.org/wiki/Man-in-the-middle_attack#Authe...

Re: Diffie-Hellman for the layman

#4

Post by 1cvmask » Sat, May 01, 2021, 3:24 AM UTC

Professor Diffie was the teacher of Taher Elgamal who helped create the Elgamal algorithm and SSL.

https://en.wikipedia.org/wiki/ElGamal_encryption

https://en.wikipedia.org/wiki/ElGamal_signature_scheme

https://en.wikipedia.org/wiki/Taher_Elgamal

Re: Diffie-Hellman for the layman

#5

Post by loudouncodes » Sat, May 01, 2021, 3:50 AM UTC

Um, he starts in 1976, then says ‘21 years later’ and he’s talking about today? He’s 20 years off in his opening premise...

Re: Diffie-Hellman for the layman

#6

Post by davidhyde » Sat, May 01, 2021, 9:29 AM UTC

> “ When WhatsApp was pressured to leave a backdoor into the encryption, it said “no” but instead agreed to log and report all dubious communication before it is encrypted. ”

Huh, I did not know that!

Re: Diffie-Hellman for the layman

#7

Post by boris1 » Sun, May 02, 2021, 6:16 AM UTC

loudouncodes wrote: post #5

Um, he starts in 1976, then says ‘21 years later’ and he’s talking about today? He’s 20 years off in his opening premise...

Thanks, gonna fix it.

Re: Diffie-Hellman for the layman

#8

Post by boris1 » Sun, May 02, 2021, 6:23 AM UTC

avmich wrote: post #2

So this doesn't unfortunately work with a man in the middle? That is, how email exchange can be guaranteed to work properly, and MITM won't insert his email in the middle of the process?

The check digits solve the MITM problem. You should compare them by another channel than email, such as text message. This is called "Short Authentication String" (SAS).

Re: Diffie-Hellman for the layman

#9

Post by boris1 » Fri, May 07, 2021, 5:37 PM UTC

I've now implemented folder encryption. If you encrypt folder 'foo', you get the file 'foo.encrypted'. When you decrypt it using the same tool, you get file 'foo.zip' which you download and uncompress into a folder 'foo'.